The invention relates to the adjustment of the coolant flow by means of a heating cut-off valve, in particular for a cooling system in a motor vehicle. During the warm-up phase of the internal combustion engine, the heating cut-off valve acting together with a three-way thermostat ensures that coolant is stationary in the coolant ducts of the engine block so that the warm-up phase of the internal combustion engine takes as short a time as possible.
The invention proceeds from a prior art as is for example known from the German patent application DE 100 12 197 A1. In this cooling system for an internal combustion engine, too, a cut-off valve in the coolant line between an engine block and a heating heat exchanger, and a three-way valve for switching between a large and a small coolant circuit, act together in order to shorten the warm-up phase of the internal combustion engine to as great a degree as possible.
For this purpose, however, the waste heat from a climate control unit is utilized in order to heat the coolant with the waste heat from the heating heat exchanger of the climate control unit when the engine is still cold.
The coolant heating from DE 100 12 197 A1 has the disadvantage that it is only effective in conjunction with a climate control unit, even this only being the case if the ambient conditions are such that a climate control unit generates an appreciable quantity of waste heat as a result of cooling activity. This is generally the case when starting a motor vehicle in summer if the vehicle has been standing in the sun. At warm ambient temperatures, however, the warm-up phase of an internal combustion engine is not very long, so that in summer, compliance with emissions limits is not a problem. These problems occur more intensely at cold ambient temperatures as are encountered in winter in the northern hemisphere. However, the climate control unit then produces no waste heat, so that the abovementioned heating of the coolant is not available when it is needed most.
DE 44 32 292 A1 discloses a cooling system for an internal combustion engine in a motor vehicle, in which the coolant flow through a heating heat exchanger is adjusted in order to assist the internal combustion engine in warming up. However, a very complex distributor device having a total of 6 valves is proposed for this purpose. The complex distributor device is necessary since the coolant pump is driven permanently and thus the coolant flow through the heating heat exchanger is required as a bypass for the disconnected coolant cooler. Three-way thermostats or three-way valves are not used. DE 44 32 292 A1 does not therefore form a generic prior art for the invention claimed here.
A number of approaches are known from the previously known prior art for shortening the warm-up phase of an internal combustion engine to as great a degree as possible. Previously, however, a permanent coolant flow has always been maintained in the engine block, even during the warm-up phase of the internal combustion engine. For this purpose, valves were used to adjust the coolant flow through the heating heat exchangers.
It is therefore an object according to the invention to further improve the control of the coolant flow through the heating heat exchangers, in order to be able to further shorten the warm-up phase of an internal combustion engine.